Roll heat-treating apparatus



April 7, 1970 J. HSONEKI ET AL 3,504,896

ROLL HEAT-TREATING APPARATUS Filed Aug. 29, 1966 5 Sheets-Shel??l 1 HgRobert L. Myers Reue/ E. Jennings Raymond D. 0r/ando April 7, 1970 FiledAug. 29. 1966 J. H. SONEK ROLL HEAT-TREATING APPARATUS 5 Sheets-Sheet 2INVENTORS Roben L. Myers Reue! E. Jennings Raymond D. Orlando -I April7, 1970 J, H SONEK;` ET Al. l 3,504,896

ROLL HEAT -TREAT I NG APPARATUS Filed Aug. 29. 1966 5 Sheets-Sheet 5 l0?A2f 7" [6 I :t -g :l 'I 'i 2e l l: :Lx-36 28 1: I: :l lI Il 1| I 34 lIif E: If/54 E: 58 :l I II ufl- /6-^.I -le =a i; /o2 It Il ii 76 l /02 IlINVENTORS -"52 [[50 Joseph H. Sone/ri Robert L. Myers Reue/ E. Jenn/n gs32 Raymond D. Or/ondo April 7, 1970 v' L H, SONEKI ET AL 3,504,896

ROLL HEAT-TREATING APPARATUS Filed Aug. 29. 1966 5 Sheets-Sheet 4 kD-HJNVEN'TORS Josep/7 H Sonek/ Rober/.Myers Reue/ E Jennings Raymond D.Orlando April 7, 1970 J. H. SONEKI ETAL 3,504,896

- ROLL HEAT-TREATING APPARATUS Filed Aug. 29. 196e 5 sheets-sheet s INVE N TORS Josep/7 H Sane/ri Rober! L. Myers Freue/ E. Jennings RaymondD. Orlando United States Patent 3,504,896 ROLL HEAT-TREATING APPARATUSJoseph H. Soneki, Bethlehem, and Robert L. Myers, Coopersburg, Pa., andReuel E. Jennings, Warren, and Raymond D. Orlando, Youngstown, Ohio,assignors to Bethlehem Steel Corporation, a corporation of DelawareFiled Aug. 29, 1966, Ser. No. 575,736 Int. Cl. C21d 1/66 U.S. Cl. 266-411 Claims ABSTRACT OF THE DISCLOSURE A carriage, vertically movable withrespect to fixed heating and quenching rings, vertically supports a rollhaving a bore therein. A coolant is forced upwardly through the borewhile the roll is progressively heated and quenched by driving the rolldownwardly through the rings. After quenching, the roll is submerged ina coolant and laterally repositioned therein.

This invention relates to the heat treatment of steel rolls, and moreparticularly to a method and apparatus for hardening the outer shell ofquench-hardenable steel rolls.

Large steel rolls are usually manufactured by forging steel into thedesired shape and then heat treating the steel shape to impart a highdegree of hardness to the outer shell thereof. In order to obtain thedesired hardness, it is necessary to heat the outer shell to atemperature above the upper critical temperature and then quench theouter shell to convert the microstructure thereof into martensite.

It is desirable for the inner portion of the roll to be tough andductile. Preferably, the heat-treating operation is controlled to insurethat the inner portion of the roll is substantially unaffected by thehardening of the outer shell.

Inasmuch as the volume of martensite is different from that of themicrostructure of the unhardened portion of the roll, stresses areintroduced into the roll by the quenching operation. If these stressesare in an unfavorable pattern, premature failure of the roll may occur.

It is an object of this invention to provide apparatus for hardening theouter shell of steel rolls whereby the stress patterns in the hardenedroll are favorable.

Another object of this invention is to provide an apparatus wherebysteel rolls can be rapidly and efficiently heat-treated.

We have discovered that the foregoing objects can be attained byvertically supporting a roll on a carriage, providing means forconcurrently heating a first annular zone of said roll and quenching asecond, contiguous annular zone of said roll, and by providingadditional means as will hereinafter be described and claimed.

Referring to the drawings:

FIGURES 1 and 2 are front and side elevations, respectively, of theapparatus of the invention.

FIGURES 3 and 4 are sectional views taken along the lines 3-3 and 4-4,respectively, of FIGURE 1.

FIGURE 5 is an enlarged front elevation showing detailed of theapparatus shown in FIGURE 1, while FIG- URES 6 and 7 are sectional viewstaken along the lines 6 6 and 7-7, respectively, of FIGURE 5.

FIGURES 8 and 9 are plan and side elevation views, respectively, showingdetails of the invention.

FIGURE 10 is a plan view showing further details of the invention.

FIGURE 1l is an enlarged front elevation of rollholding means, whileFIGURE 12 is a sectional view taken along the lines 12--12 of FIGURE 11.

Referring more particularly to FIGURES 1 and 2, a framework 10 isdisposed above a chamber 12 containing a coolant 14, e.g. water. Theframework 10 comprises a plurality of columns .16 the upper ends ofwhich are connected by longitudinal *beams 24 and by transverse beams28. The framework 10 is rigidilied by a plurality of trusses, not shown.

As shown in detail in FIGURE 3, intermediate the transverse beams 28 isa plurality of transverse supporting beams 34, 36, 38, 40, 42 and 44.Horizontally mounted on beams 38 and 40 in a bearing plate 46 upon whicha main drive motor 48, a brake 50, and a miter gear unit 52 are mounted.The miter gear unit 52 is connected, through suitable shafts andcouplings, to miter gears 54 and 56. Gear 54 is mounted on a bearingplate 58 disposed across beams 34 and 36. Gear 56 is mounted on abearing plate 60 disposed across beams 42 and 44.

Aflixed to the forward longitudinal beam 24 are supporting beams 62 and64 upon which gear reducers 66 and 68, respectively, are mounted. Thegear reducers 66 and 68 are connected to the gears 54 and 56,respectively, by suitable shafts and couplings, and are adapted to drivescrews 70 and 72, respectively. Energization of the motor 48 results inthe synchronous rotation of screws 70 and 72.

Vertically disposed above the chamber 12 are guide members 74 and 76.Similar guide members 78 and 80 are vertically disposed within thechamber 12. Guide members 74 and 78 are provided with beveled bearingsurfaces 82, while members 76 and 80 are provided with flat bearingsurfaces 84. Attached to the base of members 74 and 76 are supports 86for Abearings 88 in which the lower ends of the screws 70 and 72 aredisposed.

A carriage is adapted to be driven vertically along the framework 10.The carriage 90 broadly comprises a plurality of vertical mem-bers 92,an upper crosshead 94, a lower crosshead 96, and a plurality of trusses,not shown.

As shown in detail in FIGURE 4, mounted on the upper crosshead 94 aretwo fixed ball nuts 100 each of which threadedly engages one of thescrews 70 and 72. Suitable bearings 102, mounted on each end of theupper crosshead 94, slidably engage the bearing surfaces 82 and 84.

Mounted on the lower crosshead 96 is means 104 for supporting avertically disposed roll 106. Means 104 broadly comprises a main housing108 in which a fluid motor, not shown, is mounted. The fluid motor isadapted to rotate a bottom center post 112 in the housing 108. Thebottom center post 112 is provided with a bore, and has a conical uppersection which is adapted to be disposed in fluid-tight engagement `withthe lower end of the bore 116 of the roll 106, said lower end beingbeveled. The bottom center post 112 is provided with a plurality ofholes 118, disposed below the level of the coolant 14, through which thecoolant can flow into the bore of the bottom center post 112. Suitablebearings 117, mounted on each end of the lower crosshead 96, slidablyengage the bearing surfaces 82 and 84.

Disposed between the upper and lower crossheads is a length adjustcrosshead 120. As shown in detail in FIG- URES 5, 6 and 7, crosshead-120comprises a horizontal supporting structure 122 upon which a motor 124is mounted. The motor 124 is connected, through suitable shafts,couplings, gears, etc., to a pair of rotatable ball nuts 126 mounted onthe crosshead 120. The ball nuts 126 threadedly engage the screws 70 and72. Suitable bearings 128, attached to each end of the crosshead 120,slidably engage bearing surfaces 82 and 84. Energization of the motor124 results in vertical movement of the crosshead relative to thecarriage 90.

Mounted on the crosshead 120 is means for clamping the upper end of a'vertically disposed roll. Said means comprises a forwardly-extendinghousing 130 to which an arm 132 is pivotally connected by means ofsleeves 134 joumaled on a pin 136. Rigidly aixed to the arm 132 arebracket plates 138 to which a rod 140 is pivotally connected by means ofa pin 141. The rod 140 is connected to the piston of a hydrauliccylinder 142 which is pivotally supported in the housing 130 by bracketplates 144 and pin 145.

Mounted near the lower end of the arm 132 is a plate 146 provided with ahole 148. Mounted on the rear of crosshead 120 is a hydraulic toggleclamp 150, shown in detail in FIGURE 8, comprising a rod 152 adapted tobe driven through the hole 148 when the pivot arm 132 is in its raisedposition by reason of the retraction of rod 140. The toggle clamp 150provides positive means for maintaining the arm 132 in its raisedposition in the event that the hydraulic cylinder 142 shouldmalfunction.

Mounted on the lower end of arm 132 are clamping elements 154 and 156.Element 154 is rigidly atiixed to arm 132 while element 156 is adaptedto pivot about a fixed pivot pin 158. Element 156 is linked to a rod 160connected to the piston of a hydraulic cylinder 162 by links 164 and166. The cylinder 162 is adapted to pivot about a pin 168.

Further mounted on the length adjust crosshead 120 is means for engagingthe upper end of the bore 116 of roll 106. This means comprises abracket 170 supporting a hydraulic cylinder 172. A rod 174 connects thepiston of cylinder 172 to a supporting member 176. Member 176 Slidablyengages guides 178 and has a plate 180, containing a hole 182, affixedthereto. Mounted on the rear of crosshead 120 is a hydraulic toggleclamp 184, shown in detail in FIGURE 9, comprising a rod 186 adapted tobe driven through hole 182 when the supporting member 176 is properlypositioned relative to the roll 106.

A cylindrical housing 188 is mounted on the supporting member 176.Slidably disposed within the housing 188 is a cylinder 190. Mounted onthe lower end of cylinder 190 is a second cylinder 192. A tubular member194 extends axially through cylinders 190 and 192 and is coupled to ahollow truncated conical member 196 which is adapted to be disposed influid-tight engagement with the upper end of the bore 116 of the roll106, said upper end being beveled. Member 196 is connected to a bearingmember 198 adapted to rotate in cylinder 192.

Mounted on the front of housing 188 are bracket plates 200 to which ahydraulic cylinder 202 is ati'ixed by a pin 203. A rod 204 connects thepiston of cylinder 202 to a bracket 206 axed to a plate 208 mounted onthe cylinder 190. A guide rod 210 is attached to plate 208 and dependsthrough bearings 212 disposed in supporting member 176. Suitable means(not shown) is connected to the cylinder 202 whereby constant pressureis maintained against the roll 106 by conical member 196 during the heattreating operation.

The tubular member 194 extends through the plate 208 and bracket 206 andis connected to a rotatable joint 214 to which tubing 216 is attached.The tubing 216 is connected to a suction pump (not shown).

As shown in FIGURE l0, disposed above the coolant 14 is means forconcurrently heating a rst annular zone of the roll 106 and quenching asecond, contiguous annular zone of said roll. Said means broadlycomprises an annular heating means, e.g. an induction coil 218, disposedabove an annular quenching ring 220, said heating means and quenchingring being coaxial with said roll and mounted in position by suitablebrackets 221.

Mounted in recesses in one wall of the chamber 12 are bearing plates222, upon each of which one end of an inner rail 224 and an outer rail226 are mounted. The other ends of the rails, each of which contains asloping section intermediate first and second horizontal sections, aremounted on bearing plates 227 disposed in recesses in the opposite wallof the chamber.

A shuttle car 228 is adapted to be driven into and out of the chamber 12along rails 224 and 226. The car 228 is provided with forward wheels 230which engage the outer rails 226 and rear wheels 232 which engage theinner rails 224. The inner rails are offset from the outer rails so thatthe body of the car is always horizontal, regardless of its positionalong the rails. The rear of the car 228 is connected to a rod 234connected to the piston of a hydraulic cylinder 236.

The car 228 comprises means 238 for engaging a collar 240 disposed aboutthe neck of the roll 106. As shown in FIGURES ll and l2, the collar 240,which is adapted to engage a flange 241 on the neck of the roll 106,broadly comprises an annular structure 242 having an opening 244 thereinthrough which the neck of the roll can pass. The lower portion of thestructure 242 is provided with an inwardly-extending flange 246 havingan offset portion upon which the roll flange 241 can be seated. Thecollar is also provided with a flange 250 having a pair of eyebolts 252aixed thereto. Disposed in the flange 250 is a spring-loaded pin 254adapted to block the opening 244 when the flange 241 of the roll isproperly seated in the collar 240.

Referring again to FIGURE l0, means 238 comprises a plate 256 having arecess 258 therein adapted to receive the collar 240. An offset 260 in`plate 256 provides a shoulder upon which the flange 250 can be seated.The plate 256 is mounted on a supporting structure 262 which dependsbelow the rails 224.

The subject apparatus operates substantially as follows. Initially,i.e., prior to the loading of a roll 106 on the carriage 90, thecarriage is disposed a short distance below its uppermost position, andthe length adjust crosshead is disposed in a predetermined positionalong the carriage 90 dependent upon the length of the roll 106.Supporting member 176 is disposed in its retracted position, whilecylinder 190 is retracted within its housing 188. Pivot arm 132 is heldin its raised position by toggle clamp 150, and clamping element 156 isdisposed in its open position by reason of the retraction of the pistonof the hydraulic cylinder 162. In addition, the shuttle car 228 isdisposed in its outermost position.

The roll 106 is transported to the subject apparatus by means of a cranewhich engages the eyebolts 252 affixed to the collar 240 disposed aboutthe neck of the roll. The crane suspends the roll a short distance abovethe bottom center post 112.

The main drive motor 48 is energized to drive the carriage 90 upwardlyuntil the bottom center post 112 is in fluid-tight engagement with thelower end of the bore 116 of the roll. The toggle clamp is next releasedand the arm 132 driven about its horizontal axis until the clampingelement 154 contacts the collar 240. The clamping element 156 is thendriven into Contact with the opposite surfaces of the collar 240 bymeans of hydraulic cylinder 162.

With the roll supported on the bottom center post 112 and clamped in avertical position, the crane is disengaged from the eyebolts 252. Thesupporting member 176 is then driven horizontally until the conicalmember 196 is axially aligned with the roll 106. The toggle clamp 184 isthen actuated to cause the rod 186 to be driven through the hole 182 inthe plate 180, thereby locking the supporting member 176 in position.

The cylinder is next driven downwardly within its housing 188 until theconical member 196 is in uid-tight engagement with the upper end of thebore 116 of the roll. With the roll disposed between the bottom centerpost 112 and the conical member 196, the clamping means is rcturned toits retracted position. This is accomplished by driving the clampingelement 156 into its open position, pivoting the arm 132 into itshorizontal position, and locking the arm in said horizontal position byactuating the toggle clamp 150.

The carriage 90 is then driven downwardly until the lowest portion ofthe roll is within the contines of the induction coil 218. Next, themotor in the housing 108 is energized to cause rotation of the bottomcenter post 112,

which results in rotation of the roll 106. The suction pump then isactuated to draw the coolant 14 through the holes 118 into the bore ofthe bottom center post 112, through the bore 116 of the roll, andthrough conical member 196, tubular member 194, rotatable joint 214 andtubing 216. The coolant 14 is circulated during the heating andquenching operation.

Power, e.g., 60-cycle alternating current, is then supplied to theinduction coil 218 until the outer shell of the roll has reached theproper temperature, said temperature :being above the upper criticaltemperature. The time required for the outer shell to reach the propertemperature may, for example, be three to six minutes, depending uponthe circumference of the roll, the design of the induction coil, etc.

The carriage 90 is then driven downwardly at a speed of about 1.5 to 4.5inches per minutes. Simultanouse1y, the quenching ring 220 is actuatedto direct a quenchant onto that portion of the roll previously heated.While this portion of the roll is being quenched, a contiguous annularzone of the roll is being heated by the induction coil 218.

After the uppermost portion of the roll has been quenched, the drivemotor 48 is accelerated to rapidly cause the carriage 90 to movedownwardly so the roll is to be completely submerged in the coolant 14.The position of the carriage 90 in the coolant is such that the co1- lar240 is properly aligned with the collar-engaging means 238 of theshuttle car 228.

The motor in the housing 108 is next de-energized to stop rotation ofthe bottom center post 112 and the roll 106. In addition, the suction4pump is shut off to stop the circulation of the coolant 14 through thebore 116.

The roll 106 is then disengaged from the carriage 90 and moved awaytherefrom to a post-quench position in .the coolant 14 until thetemperature of the roll falls to below that temperature at whichtempering occurs, and preferably until the temperature of the roll fallsto about room temperature. To disengage the roll, the hydraulic cylinder236 is first actuated to drive the shuttle car 228 down the rails 224and 226 until the collar-engaging means 238 is directly below the flange241 of the collar 240. The proper position may be ascertained by meansof limit switches attached to the rails 224 and 226. Next, the carnriage 90 is driven downwardly a short distance, c g. approximately teninches, which causes the bottom center post 112 to disengage from thebore 116 of the roll and, at the same time, causes the cylinder 190 tobe driven upwardly within its housing 188. The cylinder 190 is thendriven further upwardly to bring the conical member 196 out of contactwith the bore 116 and beyond the confines of the collar 240. The shuttlecar 228 is then driven outwardly to the post-quench position byretracting the rod 234 of the hydraulic cylinder 236.

After the temperature of the roll 106 has fallen to about roomtemperature, which may take from to 60 minutes, the crane engages theeyebolts 252 of the collar 240 and raises the roll a short distance,e.g. one-half inch, to unseat the ange 250 from the collar-engagingmeans 238. The car 228 is then driven to its outermost .position and theroll raised out of the coolant 14.

Rolls heat treated in the above manner by the subject apparatus havefavorable stress patterns. In addition, the heat-treating operation israpid and efficient.

What is claimed is:

1. Apparatus for heat treating a quench-hardenable ferrous metal rollcomprising:

(a) a carriage;

(b) means mounted on said carriage for supporting the lower end of avertically disposed roll;

(c) means for clamping said roll;

(d) means adapted to be driven into axial alignment with said -roll anddriven vertically into engagement with the upper end of said roll;

(e) means for concurrently heating a first annular zone 6 of said rolland quenching a second, contiguous annular zone of said roll; and

(f) means for moving said carriage relative to means (e) until thedesired surfaces of said roll have been heated and quenched.

2. Apparatus as recited in claim 1, in which means (c) is adapted to Ibepivoted about a horizontal axis and comprises two clamping elements oneof which is adapted to be pivoted about a vertical axis into and out ofcontact with said roll.

3. Apparatus for heat treating a quench-hardenable ferrous metal roll,comprising:

(a) a carriage;

(b) mans mounted on said carriage for supporting a ro (c) means movablewith said carriage for clamping said roll with its axis verticallydisposed and for engaging the upper end of said roll;

(d) said means (c) including means adapted to be drlilven horizontallyinto axial alignment with said ro (e) means for concurrently heating afirst annular zone of said roll and quenching a second, contiguousannular zone of said roll; and

(f) means for moving said carriage relative to means (e) until thedesired surfaces of said roll have been heated and quenched.

4. Apparatus for heat treating a quench-hardenable ferrous metal roll,comprising:

(a) a carriage;

(b) means mounted on said carriage for supporting the lower end of avertically disposed roll;

(c) means movable With said carriage adapted to be driven verticallyrelative to said carriage;

(d) clamping means disposed on means (c), including means adapted to bepivoted about a horizontal axis, said clamping means further includingtwo clamping elements one of which is adapted to be pivoted about avertical axis into and out of contact with said roll;

(e) means, disposed on means (c), adapted to be driven into axialalignment with said roll and driven vertically into engagement with theupper end of said roll;

(f means for concurrently heating a first annular zone of said roll andquenching a second, contiguous annular zone of said roll; and

(g) means for moving said carriage` relative to means (f) until thedesired surfaces of said roll have been heated and quenched.

5. Apparatus for heat treating a quench-hardenable ferrous metal rollhaving a bore therein, comprising:

(a) a carriage;

(b) means mounted on said carriage for vertically supporting a roll,comprising a first tubular member in fluid-tight engagement with thelower end of the bore of said roll;

(c) means movable with said carriage for clamping said roll with itsaxis vertically disposed and for engaging the upper end of said roll;

(d) said means (c) including means adapted to be driven into axialalignment with said roll comprising a second tubular member adapted tobe disposed in fluid-tight engagement with the upper end of the bore ofsaid roll;

(e) means for circulating a fluid through said tubular members and saidbore;

(f) means for concurrently heating a rst annular zone of said roll andquenching a second, contiguous annular zone of said roll; and

(g) means for moving said carriage relative to means (f) until thedesired surfaces of said roll have been heated and quenched.

6. Apparatus for heat treating a quench-hardenable ferrous metal rollhaving a bore therein, comprising:

(a) a carriage;

(b) means mounted on said carriage for vertically supporting a roll,comprising a first tubular member in fluid-tight engagement with thelower end of the bore of said roll;

(c) means movable with said carriage adapted to be driven verticallyrelative to said carriage;

(d) clamping means, diposed on means (c), including means adapted to bepivoted about a horizontal axis, said clamping means further includingtwo clamping elements one of which is adapted to be pivoted about avertical axis into and out of contact with said roll;

(e) means, disposed on means (c), adapted to 'be driven vertically intoengagement with the upper end of said roll comprising a second tubularmember adapted to be disposed in uid-tight engagement with the upper endof the bore of said roll;

(f) means for circulating a uid through said tubular members and saidbore;

(g) means for concurrently heating a first annular zone of said roll andquenching a second, contiguous annular zone of said roll; and

(h) means for moving said carriage relative to means (g) until thedesired surfaces of said roll have been heated and quenched.

7. Apparatus lfor heat treating a quench-hardenable ferrous metal roll,comprising:

(a) a carriage;

(b) means mounted on said carriage for supporting a vertically disposedroll;

(c) means movable with said carriage for engaging the upper end of saidroll;

(d) said means (c) including means adapted to be driven into axialalignment with said roll;

(e) said means (c) including means for maintaining constant pressureagainst said roll;

(f) means for concurrently heating a rst annular zone of said roll andquenching a second, a contiguous annular zone of said roll; and

(g) means for moving said carriage relative to means (f) until thedesired surfaces of said roll have been and quenched.

8. Apparatus for heat treating a quench-hardenable steel roll,comprising:

(a) acarriage;

(b) rlneans mounted on said carriage for supporting a rol (c) meansmovable with said carriage for clamping said roll with its axisvertically disposed and for engaging the upper end of said roll;

(d) said means (c) including means adapted to be driven into axialalignment with said roll;

(e) said means (c) including means for maintaining constant pressureagainst said roll;

(f) means for concurrently heating a first annular zone of said roll andquenching a second, contiguous annular zone of said roll; and

(g) means for moving said carriage relative to means (f) until thedesired surfaces of said roll have been heated and quenched.

9. Apparatus for heat treating a qucnch-hardenable ferrous metal roll,comprising:

(a) acarriage;

(b) means mounted on said carriage for supporting a roll;

(c) means movable with said carriage adapted to be driven verticallyalong said carriage;

(d) clamping means, disposed on means (c), including means adapted to bepivoted about a horizontal axis, said clamping means further includingtwo clamping elements one of which is adapted to be pivoted about avertical axis into and out of contact with said roll;

(e) means, disposed on means (c), for engaging the upper end of saidroll and maintaining constant pressure thereagainst, including meansadapted to be driven into axial alignment with said roll;

(f) means for concurrently heating a rst annular zone of said roll andquenching a second, a contiguous annular zone of said roll; and

(g) means for moving said carriage relative to means (f) until thedesired surfaces of said roll have been heated and quenched.

10. Apparatus for heat treating a quench-hardenable ferrous metal roll,comprising:

(a) a vertically movable carriage;

(b) means mounted on said carriage for vertically supporting a roll;

(c) a chamber containing a coolant disposed in the path of saidcarriage;

(d) means mounted above said chamber for concurrently heating a rstannular zone of said roll and quenching a second, contiguous annularzone of said roll',

(e) means for driving said carriage vertically until said roll iscompletely immersed in said coolant; and

(f) means for engaging said roll while immersed in said coolant andlaterally re-positioning said roll in said coolant.

11. Apparatus as recited in claim 5, in which means (e) comprisessuction means adapted to draw said fluid upwardly through the bore ofsaid roll.

References Cited UNITED STATES PATENTS 2,146,793 2/1939 Buckner 14s-14s2,317,233 4/1943 Taylor zes- 6x 3,271,019 9/1966 Armstrong 266-6 X I.SPENCER OVERHOLSER, Primary Examiner J. S. BROWN, Assistant ExaminerU.S. Cl. X.R. 148-148 UNITED STATES PATENT OFFICE CERTIFICATE 0FCORRECTION Patent No. 3 ,504 ,896 April 7 1970 Joseph H. Sonek et al Itis certified that error appears in the above identified patent and thatsaid Letters Patent are hereby` corrected as showfm below:

Column l, line 24, cancel "a method and". Column 2, line I9, "beams"should read means Column 5, line 24, cancel "to be".

Signed and sealed this 25th day of August 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

